Norrie disease is an X-linked recessive condition in which blindness is invariable, mental retardation is common and deafness is usually present. The ocular findings include totally detached fibrotic retinas with subsequent cataracts, corneal clouding and shrinkage of the globe. A close linkage has been found between Norrie disease and locus- DXS7 on the short arm of the X chromosome (Xp11.3). The combined lod score for 0=0 is Z=9.32. Two unrelated patients with Norrie disease and deletion of DXS7 locus without chromosomal abnormality have been identified. We have recently found a patient with deletion of at least 10 kb at the DXS7 locus in a pedigree with Norrie disease and provided prenatal diagnosis. The goal of this proposal is to clone the gene that is responsible for Norrie disease. The following experimental approaches will be employed in order to clone this gene: 1. Chromosomal walking and jumping from locus DSX7 and isolation of several single copy DNA fragments to use as probes against DNA from the patient until a probe is found that identifies an abnormal (junction) DNA fragment in be patient after routine electrophoresis or PFGE. 2. PERT reaction to isolate more DNA fragments from the deleled ares. 3. After the identification of a junction DNA fragment, the size of the deletion will be estimated and single copy probes from the deleted DNA will be used to identify (i) RNAs from different tissues from human and other species (ii) cDNAs from fetal brain and adult retina libraries. 4. The cDNAs from the deleted areas will be used as probes against DNAs from several mammalian species. The nucleotide sequences will be determined and the predicted protein(s) will be further studied. The association of the protein(s) and Norrie disease will also be studied.